1. Field of the Invention
The present invention relates to a congestion control system, and more particularly to a congestion control system capable of detecting congestion occurring in an Asynchronous Transfer Mode (ATM) network for transferring connectionless traffic and autonomously avoiding the congestion.
2. Description of the Related Art
Recently, attention is being given to an ATM communication as a high-speed communication technique or a scalable wide-band transfer technique making good use of resources such as terminals introduce by a user on the basis of the communication technique of the existing LAN (Local Area Network) such as Ethernet. In this ATM communication, cell for dividing the transfer data with the transfer control information including the destination information attached thereto by the fixed length is defined as the unit of transfer and these cells are transferred to a network of the destination while passing on the respective ATM switches.
However, if using this ATM communication heavily in the field of the information communication, disadvantages such as abandonment of transfer data may occur due to the congestion caused by an increase of transfer information amount and overload on a node, thereby increasing the importance of technology for relieving the congestion.
In order to relieve the congestion, there is known a congestion control system for controlling traffic on a corresponding connection depending on the congestion state notified by the ATM network, at the entrance of receiving transfer packets for a network such as the ATM network. In this system, a virtual communication channel which is inevitably decided from a plurality of Virtual Path Identifiers (VPI) and Virtual Channel Identifiers (VCI) established on the identical transfer channel is defined as a connection group.
Since the ATM communication can establish a virtual communication channel inevitably decided from a plurality of VPIs and VCIs, within a physical line or a virtual path, it can make efficient use of the resources while restraining the cell abandonment at the minimum on a connection having the congestion occurrence.
FIG. 14 is a view for use in describing the principle of the conventional congestion control system. In this congestion control system, the respective transfer packets are transferred from a plurality of connections 201a, 201b, and 201c via a connection group 202 to a network 203. Connection monitoring means 204a, 204b, and 204c are adopted to monitor the transfer packets flowing from the respective connections 201a, 201b and 201c to the connection group 202 and the flow amount of the transfer packets. A connection group monitoring means 205 is adopted to monitor the transfer packets transferred to the connection group 202 and monitor the flow amount of the transfer packets in every connection group defined by a connection group defining means 206.
The control means 207 can switch the control between monitor mode and control mode, so to control the connection monitoring means 204a, 204b, and 204c and the connection group monitoring means 205. The monitor mode is an operation mode for monitoring whether the flow amount of a transfer packet is beyond a predetermined threshold or not. The control mode is an operation mode for abandoning the extra packets when the flow amount of the transfer packets is beyond the threshold, and controlling the priority of abandonment by the cell loss priority (CLP) display.
In the non-congestion state, the connection monitoring means 204a, 204b, and 204c are operated in a monitor mode and the connection group monitoring means 205 is operated in a control mode. Namely, packets to be transferred from the connection group 202 to the network 203 are controlled and their flow amount is controlled by every connection group, so as not to cause the congestion within the network 203.
In the congestion state, a connection on which the packet flow amount is beyond the threshold is recognized, based on the monitoring result from the connection monitoring means 204a, 204b, and 204c monitoring the flow amount of the respective packets of the respective connections 201a, 201b, and 201c. One of the connection monitoring means 204a, 204b, and 204c corresponding to the connection is switched to a control mode. In the other words, the packet flow amount is controlled only on a congested connection.
A congestion control technique for performing the flow control of traffic called polishing at the entrance of a network of the above-mentioned congestion control system is disclosed in, for example, Japanese Patent Publication Laid-Open (Kokai) No. Heisei 9-149046, xe2x80x9cPacket Flow Amount Monitoring/Controlling Methodxe2x80x9d.
Further, a technique for performing the dynamic control of traffic within ATM switches dispersedly arranged in a network, instead of the flow control of the traffic at the entrance of a network, is disclosed in, for example, Japanese Patent Publication Laid-Open (Kokai) No. Heisei 8-204721, xe2x80x9cCongestion Control Method in Asynchronous Transfer Mode Networkxe2x80x9d.
The conventional congestion control system is only to relieve congestion by monitoring the transfer flow only at the entrance of a network or within an ATM switch. It is not to make good use of resources of the whole network.
Namely, the technique disclosed in Japanese Patent Publication Laid-Open (Kokai) No. Heisei 9-149046, in which the flow control of traffic is performed at the entrance of a network, has to define every expected traffic as a connection group. Therefore, it is difficult to apply this technique to the traffic having the difficulty of defining the quality and having the dynamically changing volume like connectionless traffic. Even if applying this technique to such traffic, complicated processing will be required in order to assign the network resources efficiently.
The technique disclosed in Japanese Patent Publication Laid-Open (Kokai) No. Heisei 8-204721, in which the dynamic control of traffic is performed only within an ATM switch, requires complicated processing for the optimal control of the add-on device and ATM switches dispersedly arranged according to the transfer situation therebetween, in order to monitor traffic on the whole network and control congestion. It is difficult to apply the technique to the whole network.
The ATM forum recommends ABR (Available Bit Rate) regulation in an ATM network as a technique for dynamically assigning the resources of a network on a predetermined fixed channel to the respective traffic. This ABR regulation, however, requires the traffic control between terminals by the flow unit, thereby needing building a complicated network system and an edge device. Further, since the regulation includes neither a method of dynamically changing a channel nor condition of changing a channel, it cannot make use of the network resources dynamically and efficiently, or even if making use of the resources, complicated and sophisticated processing will be required.
A first object of the present invention is to provide a congestion control system capable of detecting congestion occurring in an ATM network, with respect to connectionless traffic, in a simple structure, so to relieve the congestion, thereby making use of the network resources efficiently.
A second object of the present invention is to provide a congestion control system capable of detecting congestion caused by outside blocking occurring on the boundaries of a user network and an ATM network for transferring connectionless data, with an easy operation, and further capable of autonomously relieving congestion caused by the outside blocking, in a simple structure.
A third object of the present invention is to provide a congestion control system capable of detecting congestion caused by inside blocking as second congestion when no congestion caused by the outside blocking is detected as the first congestion and autonomously relieving the congestion caused by the inside blocking.
A fourth object of the present invention is to provide a congestion control system capable of autonomously relieving congestion caused by outside blocking, in a simple structure free from complicated and enormous network equipment.
A fifth object of the present invention is to provide a congestion control system capable of autonomously relieving congestion caused by inside blocking as the second congestion, which cannot be relieved only by the change of a transfer channel.
A sixth object of the present invention is to provide a congestion control system capable of changing a transfer channel easily and flexibly by use of loose source routing in order to relieve congestion caused by inside blocking, without changing setting of a relay node within an ATM network, and capable of simplifying the structure of a relay node.
According to one aspect of the invention, a congestion control system for detecting and relieving congestion occurring in a network system including an ATM network, a source user network for sending a transfer packet in asynchronous transfer mode, and a destination user network for receiving the transfer packet from the source user network, the congestion control system comprises
average flowing speed measuring means for measuring average flowing speed of a transfer packet flowing from the source user network, for every destination user network,
first congestion detecting means for detecting first congestion occurring when the total sum of the average flowing speed of every source user network is greater than the transfer speed toward the destination user network,
permissible flowing speed calculating means for calculating permissible flowing speed of a transfer packet flowing from the source user network, based on the total sum of the average flowing speed and the transfer speed and establishing the permissible flowing speed, and
flowing speed control means for controlling the average flowing speed of a packet flowing from the source user network under the permissible flowing speed when detecting first congestion by the first congestion detecting means.
In the preferred construction, the measured average flowing speed is notified to the first congestion detecting means and the permissible flowing speed calculating means by a first congestion controlling packet for controlling congestion, and the first congestion detected by the first congestion detecting means is notified to the flowing speed control means by a second congestion controlling packet which is returned in reply to the first congestion controlling packet.
In another preferred construction, the average flowing speed measuring means and the flowing speed control means are mounted on a source edge device provided in every source user network, on the boundaries of the ATM network and the source user network, and the permissible flowing speed calculating means and the first congestion detecting means are mounted on a destination edge device provided in every destination user network, on the boundaries of the ATM network and the destination user network.
In another preferred construction, the average flowing speed measuring means and the flowing speed control means are mounted on a source edge device provided in every source user network, on the boundaries of the ATM network and the source user network, the permissible flowing speed calculating means and the first congestion detecting means are mounted on a destination edge device provided in every destination user network, on the boundaries of the ATM network and the destination user network, the source edge device writes the measured average flowing speed into the first congestion controlling packet for controlling congestion and notifies the packet to the destination edge device, and the destination edge device writes the first congestion detected by the first congestion detecting means into the second congestion controlling packet to be returned in reply to the first congestion controlling packet and notifies the packet to the source edge device
In another preferred construction, the permissible flowing speed of every transfer packet flowing from a plurality of the source user networks is set at the same speed.
According to another aspect of the invention, a congestion control system for detecting and relieving congestion occurring in a network system including an ATM network, a source user network for sending a transfer packet in asynchronous transfer mode, a destination user network for receiving the transfer packet from the source user network, and relay nodes relaying a transfer packet to be transferred between the source user network and the destination user network, the congestion control system comprises
average flowing speed measuring means for measuring average flowing speed of a transfer packet flowing from the source user network, for every destination user network,
first congestion detecting means for detecting first congestion occurring when the total sum of the average flowing speed of every source is greater than the transfer speed toward the destination user network,
permissible flowing speed calculating means for calculating permissible flowing speed of a transfer packet flowing from the source user network, based on the total sum of the average flowing speed and the transfer speed,
flowing speed control means for controlling the average flowing speed of a packet flowing from the source user network under the permissible flowing speed when detecting first congestion by the first congestion detecting means,
inside node congestion detecting means for detecting inside node congestion occurring when the transfer speed of a packet received at the receiving side of the relay node is greater than the transfer speed at the sending side of the relay node,
second congestion detecting means for detecting second congestion occurring when the inside node congestion detecting means detects the inside node congestion and the first congestion detecting means detects none of the first congestion,
transfer channel database for storing transfer channel information indicating transfer channels corresponding to the transfer from the source user network to the destination user network,
transfer channel retrieving means for retrieving a transfer channel possible to avoid a relay node having the inside node congestion detected by the inside node congestion detecting means, from the transfer channel database, when detecting the second congestion by the second congestion detecting means, and
transfer channel control means for controlling the transfer based on a transfer channel retrieved by the transfer channel retrieving means.
In the preferred construction, the measured average flowing speed is notified to the first congestion detecting means and the permissible flowing speed calculating means by a first congestion controlling packet for controlling congestion, and the first congestion detected by the first congestion detecting means and the detection result by the inside node congestion detecting means are notified to the flowing speed control means, the second congestion detecting means, and the transfer channel retrieving means by a second congestion controlling packet which is returned in reply to the first congestion controlling packet.
In another preferred construction, the average flowing speed measuring means, the flowing speed control means, the second congestion detecting means, and the transfer channel control means are mounted on a source edge device provided in every source user network, on the boundaries of the ATM network and the source user network, the permissible flowing speed calculating means and the first congestion detecting means are mounted on a destination edge device provided in every destination user network, on the boundaries of the ATM network and the destination user network, and the transfer channel database and the transfer channel retrieving means are provided in a network monitor for monitoring the congestion state within the ATM network.
In another preferred construction, the average flowing speed measuring means, the flowing speed control means, the second congestion detecting means, and the transfer channel control means are mounted on a source edge device provided in every source user network, on the boundaries of the ATM network and the source user network, the permissible flowing speed calculating means and the first congestion detecting means are mounted on a destination edge device provided in every destination user network, on the boundaries of the ATM network and the destination user network, the transfer channel database and the transfer channel retrieving means are provided in a network monitor for monitoring the congestion state within the ATM network, the source edge device includes notifying means for writing the measured average flowing speed into the first congestion controlling packet for controlling congestion and notifying the packet to the destination edge device via the relay node having the inside node congestion detecting means, and the destination edge device includes notifying means for writing the first congestion detected by the first congestion detecting means and the detection result by the inside node congestion detecting means into the second congestion controlling packet to be returned in reply to the first congestion controlling packet and notifying the packet to the source edge device and the network monitor.
In another preferred construction, the relay node includes notifying means for writing the detection result of the inside node congestion by the inside node congestion detecting means into the first congestion controlling packet and notifying the packet to the destination edge device.
In another preferred construction, the congestion control system further comprises resource changing means for changing resources assigned for the transfer from the source user network to the destination user network, and resource change requesting means for requesting the resource changing means to change the resource assignment when the second congestion detected by the second congestion detecting means is not relieved by the transfer channel control means changing a transfer channel by the transfer channel control means.
In another preferred construction, the permissible flowing speed of every transfer packet flowing from a plurality of the source user networks is set at the same speed.
In another preferred construction, the transfer channel control means changes a transfer channel according to loose source routing so as to control the transfer.
Other objects, features and advantages of the present invention will become clear from the detailed description given herebelow.